【1】源代码
1 #include2 #include 3 4 class Student 5 { 6 public: 7 Student(int id, QString name, int status) 8 : m_nID(id) 9 , m_name(name)10 , m_status(status)11 {}12 13 int getId()14 {15 return m_nID;16 }17 void setId(int id)18 {19 m_nID = id;20 }21 22 QString getName()23 {24 return m_name;25 }26 void setName(QString name)27 {28 m_name = name;29 }30 31 int getStatus()32 {33 return m_status;34 }35 void setStatus(int status)36 {37 m_status = status;38 }39 40 QString toString()41 {42 return QString("Student [id = %1, name = %2, status = %3]")43 .arg(QString::number(m_nID)).arg(m_name).arg(QString::number(m_status));44 }45 46 public:47 static const int INVALID;48 static const int VALID;49 50 private:51 int m_nID;52 QString m_name;53 int m_status;54 };55 56 const int Student::INVALID = 0;57 const int Student::VALID = 1;58 59 void main()60 {61 Student *pStudent = new Student(1, "张三", Student::VALID);62 qDebug() << pStudent->toString();63 }64 65 // run out:66 /*67 * "Student [id = 1, name = 张三, status = 1]"68 */
【2】以类取代类型码
1 #include2 #include 3 4 class StatusCode 5 { 6 public: 7 StatusCode(int nCode) 8 : m_nCode(nCode) 9 {}10 11 int getCode()12 {13 return m_nCode;14 }15 16 void setCode(int code)17 {18 m_nCode = code;19 }20 21 QString toString()22 {23 return QString("StatusCode [code = %1]").arg(QString::number(m_nCode));24 }25 26 private:27 int m_nCode;28 };29 30 class Student31 {32 public:33 Student(int id, QString name, StatusCode status)34 : m_nID(id)35 , m_name(name)36 , m_status(status)37 {}38 39 int getId()40 {41 return m_nID;42 }43 void setId(int id)44 {45 m_nID = id;46 }47 48 QString getName()49 {50 return m_name;51 }52 void setName(QString name)53 {54 m_name = name;55 }56 57 StatusCode getStatus()58 {59 return m_status;60 }61 void setStatus(StatusCode status)62 {63 m_status = status;64 }65 66 QString toString()67 {68 return QString("Student [id = %1, name = %2, status = %3]")69 .arg(QString::number(m_nID)).arg(m_name).arg(m_status.toString());70 }71 72 private:73 int m_nID;74 QString m_name;75 StatusCode m_status;76 };77 78 void main()79 {80 Student *pStudent = new Student(1, "张三", StatusCode(1));81 qDebug() << pStudent->toString();82 }83 84 // run out:85 /*86 * "Student [id = 1, name = 张三, status = StatusCode [code = 1]]"87 */
【3】总结
类中有一个数值类型码，但它并不影响类的行为。以一个新的类替换该数值类型码。
在使用Replace Type Code with Class （以类取代类型码）之前，你应该先考虑类型码的其他替换方式。
只有当类型码是纯粹数据时（也就是类型码不会在switch语句中引起行为变化时），你才能以类来取代它。
更重要的是：任何switch语句都应该运用Replace Conditional with Polymorphism （以多态取代条件表达式）去掉。
为了进行那样的重构，你首先必须运用 Replace Type Code with Subclass （以子类取代类型码）或Replace Type Code with State/Strategy （以状态策略取代类型码），把类型码处理掉。
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